Safety valve



Jai 28, 1947. T, w, BERGQUBT 2,414,794

SAFETY VALVE Filed Dec. 13, 41944A 2 sheets-sheet 1 /f/QZ i 4 fw fw 7 Z,wd M M 4 w .4-- J w- 5 m. an@ z 7 5 ET @mvg v. 4 9M M M w j M71@ o mw.IW 2( 4 w .ww 2 mw A HJ .l /rlm%w\\ 4 4 4 .uv Il w M @7- 4 M w T. W.BERGQUIST SAFETY VALVE Filed Dec. 13. 1944 ..45 w H wacm w. wv w ./bw M@Z5 IW @Lw y. www? J Mw Patented Jan. 28, 1947 SAFETY VALVE Theodore W.Bergquist,

signorl to Willow Grove, Pa., as- J. E. Lonergan Company, Philadelpilla,Pa.. a corporation oi Pennsylvania` Application December 13, i944,Serial No. 567,955

2Y claims. (ci. isi-53) 4 This invention relates to safety valves forpressure fluid systems, reservoirs, pressure generators, etc.; and thepresent application constitutes a continuation-impart of my priorapplication Serial No, 524,049, filed February 26, 1944.

The primary object of the invention is to provide a relief or safetyvalve which will embody certain improved structural features aordingnumerous operating advantages over valves of the prior art. such ashigher lift, lower blowdown, greater stability, greater protection forthe system or vessel to which the valve is applied, less stress' on theseating surfaces ofthe valve, higher discharge capacity,.elimination oi'drumming, elimination of sudden and violent preseure uctuations, and soforth.

The' ioregolng structural improvements and resultant advantages will bereadily understood from the following description, with reference to theaccompanying drawings, of which:

Fig. l is a longitudinal sectional elevation of the preferred form ofvalve;

Fig. Z is a sectional plan view taken on the line d-i in Fig. l;

Fiss. d, d, 5 and 6 are fragmentary longitudinal sectional elevationsdiagrammatically illustrating the principal portions of the valve shownin Fig. i in dicrent relative positions during one cycle ci'operation-of the valve.

As shown in Figs. l and 2 of the drawings, the valve of the presentinvention comprises a valve body i, in which is formed avmain chamber t,an

inlet duct t. an outlet or discharge duct 4, and a complementary chamber5 which is axially aligned with the inlet duct 3.

The outlet duct d and the complementary chamber 5 are in directcommunication with the main chamber 2, while-the inlet duct 3 hascommunication with the .main chamber 2 only through a hollowfrusto-conical nozzle t having an intermediate annular external portionthere- Y of threaded into a correspondingly threaded annular internalcounterbore l formed in the duct 3. The inner end of the nozzle t isprovided with an annular. axial extension il having a narrow thatcircular end face 9 disposed in a plane at right angles to the axis ofthe nozzle 6, and which constitutes the seat of the valve.

Below the annular axial extension B, the nozzle 3 is externally threadedto receive internal threads ot an adjustable warn ring I0. The ring Itis provided with a relatively wide ilat annular end face Il, which likethe valve seatV 9 is also at right angles to the axis of the nozzle 8.The wide ilatiace i I of the nozzle-encircling ring l0 is adapted lllfor adjustment to various planes parallel to the plane of the encircledvalve seat 9, axially of the nozzle S.

An annular recess i2 is formed by and'between the inner circumferentialedge of the fiat annular end-face' il of the ring i0 andthe outercircumferential edge of the flat annular end face of the axial extensiont on the nozzle t which forms the valve seat t.

The outer end ofthe complementary chamber t is counterbored at i3, forthe reception of a corresponding external annular flange M formed on acylindrical piston guide l5, which latter projects into the main chamber2.

Adjacent its inner end, theV cylindrical guide ring man opposite dat endil oi which is adapted to be adiustably right angles to it, parallel tomaintained in a plane at the axis of the cylindrical guide and spaced apredetermined distance from the plane of the valve seat t, axially ofthe chamber 2.

The control ring it is axially adjustable relative to the cylindricalpiston guide l5 to vary the distance between the plane of the innercircular edge i8 of its lower face and the plane of the valve seat t.

Blidably mounted within the piston guide I5, for axial movement inopposite directions therein, is a valve piston 20, which is providedwith a substantially :dat end face 2l disposed in a plane substantiallyat right angles to the coinciding axes oi the piston 20 and itssurrounding guide l5.

In the center of the endiace 2l of the piston i@ is a. downwardlyprojecting spreader cone 22, by which dowing fluid impinging against thesuriace 2l 'of the piston 2li is directed radially outward, in alldirectionaltoward an annular rib 23 which is formed on the surface 2|concentric to the axis of the piston 20.

The rib 23 is provided with a dat circular narrow face' 24 ofsubstantially the same inside and outside diameter as the dat circularface 8 of the valve seat, against which the circular face 2li is adaptedto bear and to register, concentrically. to close off ow of pressurefluid from the bore of the nozzle 5 into the valve chamber 2.

'.Ihe piston 20 is of greater diameter than the ring lil and is providedwith an axially projectlng skirt or cape 25 which circumferentiallyencircles the outer peripheral edge 26 of the flat annular surface Il ofthe ring l0, and extends 20 over a substantial portionof the axiallength of the ring l0.

The inner surface 21 of the skirt 25 is of a frusta-conical form andflares radially outward f from a circle 28 describing the intersectionof l the frusto-conical surface 21 of the skirt 25 with the fiat headsurface 2| of the piston 20, which circle 28 is of slightly greaterdiameter than the peripheral edge 26 ofthe ring l0.

The piston seating surface 24 is normally maintained in contact with thevalve seat 9, by a loading spring 30 which is housed in a substantiallycylindrical spring casing 3|, which latter is provided at one end with ahead plate 32. The plate 32 is adapted tobe secured to the valve bodyaround the complementary chamber 5, in any suitable manner, as by bolts,screws, etc.

The piston 20 is provided with a suitable stem 35 having one end 36rounded and seated in an internally threaded axial recess 31 formed inthe solid end portion or head 38 of the piston 2li.

The piston stem or rod 35 has radially extending pins 39, 33 whichextend radially outward from the piston stem 35 into the recess belowthe lower end of a star nut 40 threaded in the re- `cess 31.

Thepiston vstem or rod 35 projects from the head 38 of the pistonaxially through the hollow body thereof, the guide and the end plate 32of the spring case 3|, into and through the cylindricalv spring case 3|.The second endA of the rod 35 is slidably mounted in an axial boreformed in an adjusting screw di which i's threaded into a hub or boss 42formed at and closing the second end of the spring case 3|.

Mounted on and resting against an annular lshoulder t3 on the stem35,-within the hollow spring casing 3|, is a spring abutment washer @dagainst which one end of the loading spring 35 bears, the opposite endof said spring bearing against a loose abutment washer 45 slidablymounted on the stem 35 and which rests against the inner end of theadjusting screw 5|.

The loading spring 35 may be set to any'desired popping pressure of thevalve, by proper adjustment of the screw 4|, and the screw is secured inits adjusted position by a jamb nut (i6. A cap 41 covers the adjustingscrew and its lock nut and is removably secured`on the periphery of acentral boss' t2 in which the adjusting screw 4| is mounted.

As shown in Figs. 1 and 2, the closed end 33 oi the piston 20" isprovided with a deep circumferential groove in the form `of asubstantially annular recess` 5|] which produces an annular flange-likeportion 5| on the end of the piston 20. The flange 5| has an innersurface 52 substantially parallel to and axially spaced from the endsurface 2| of the piston 20, and where `the vflange surface 52intersects with the peripheral surface of the piston 20 a relativelysharp cutoff edge 53 is formed to cooperate with the sharp inner`circular edge I8 of the control ring |6 for purposes hereinafterdescribed.

Ports 54, 54 are formed in and extend through circular seating face 24from the circular valve.l l

, 55 formed by and between the broad flat annular surface 1| of the ringi0 and the opposed similar broad at annular face 2| of thegange 5| onthe piston 20.

A portion of the pressure fluid entering the annular space 55 escapestherefrom through the ports 54 from the under Aside of the ange 5| tothe upper side thereof, into the substantially annular space 50 in thepiston 20, and from this space 50 into 'the valve chamber 2 through acircular port c formed by' and betweentthe inner sharp circular edge i3of the control ring I6 and the sharp peripheral edge 53 of the flange5|.

The flat annular face 2| of the under side of the piston flange 5| andthe frusto-conical surface 21 of the piston skirt 25, combined, form abaille against which the pressure fluid escaping through the annulardischarge port a reacts.

At the instant of initial popping of the valve, (100% of the set"pressure) the effects of the skirted baille aiorded by thefrusto-conical surface 21 are substantially nil and the lifting of thevalve is then primarily effected by the eX- pansion of the pressurefluid in the annular chamber 55. However'as soon as the valve is liftedto an appreciable extent the effective area of the skirted bailleincreases progressively, as the surface 21 moves upwardly to a greaterextent beyond and with respect to the sharp peripheral edge 25 of theflat annular surface I of the warn ring lli, between which and thedownwardly'flar- :lng surface 21 of the skirt 25 is formed an escapeport b.

As shown in Eig. 3, just before the valve pops, the port a is fullyclosed, the port b is substantially closed as no contact between theedge 25 and surface 21 is ever actually effected, and the port c isfully open.

When the valve pops, the pressure fluid escaping through the partiallyopened port a expands in the annular space 55 and starts to raise thevalve. of the port b progressively increases andthe port c progressivelycloses until the 4position of Fig. e is reached, wherein the ports a andb are substantially 75% open and the port c is practically closed.

The fluid pressure reacting against. the constantly increasing area ofthe baille surface of the piston raises the valve until the port c isentirely closed, cutting off upward escape of the flange 5| of thepiston 20 from the end face y 2| thereof to the face 52 of the annularrecess 5U.

In operation of the valve shown in Figs. 1 and 2, the loading spring 30is .set, by adjusting the screw 4|, to any desired pressure at which thesafety valve is to .pop or blow-off, i. e. the pressure at which, forexample 100# per square incli`,'actng against the head face 2| of thepiston 20, the piston will rise slightly from its fully from beneathpiston 20.

The full force of the pressure fluid passing through the port a, whichhas reached substantially 103% of the set pressure, then becomeseffective to raise the valve to its full open position shown in Fig. 5wherein the ports a and b` are fully open with thepressure reactingagainst the full area of the baille surface formed by the combined areasof' the annular surface 2| and the frusto-conical surface 21 of thepiston.

The full force of the fluid pressure acting against the full area of`the bailleI surface maintains the valve in its fully open positionuntil the pressure in the vessel or system to which the valve isconnected begins to drop. As the medium in the vessel is relieved thepressure As the valve piston 21| rises the openingv under the pistondecreases and accordingly the lift diminishes rapidly until the`pressure'has dropped to substantially 97% oi the set pressure, at whichpoint thevaive is ready to close abruptly. The piston 2n descends underthe.

iniiuence of the loading spring 30 as a result of the decrease inthe-pressure of the fluid in the nozzle 5, whereupon the port c opens,as shown in Fig'. 6, and permits the pressure iiuid to escape from underthe piston through the ports 54 in the ilange 5l into the annular recessing port c.

As the port c opens, the port b closes, resulting in ,a vrapidlydecreasing effective baille area i turnins the ring It up or down thepressure at which the valve closes can be regulated to suit4 conditions.Il the valve closes at e. pressure higher than desired the ring can beturned dovm closer to the edge ed of the piston dance 5i and therebycause the valve to remain longer od its seat. Conversely, if thereclosinig pressure is too lov.r the ring is turned up, i. e. furtheraway from edge @t of the piston flange di. l

By moving the control ring it' axially to bring the edge ld thereofcloser to or further away from the edge tt ci the piston flange El, thepressure at which the piston t@ returns to its seat can be accuratelycontrolled and this with the cushioning eflect obtained by properadjustment of the warn ring i@ prevents the valve from closing with: theforce of a hammer blow which would lbe. injurious to the seatingsurfaces of the valve and piston. V

When the correct adjustment of the ring i0 is attained it may be lookedin position by a' ring pin de which has an enlarged outer end dithreaded Iinto and through the shell of the valve body l, and arelatively pointed inner end et entering longitudinal flutes et in thelovver portion of the periphery ci the ring lll.

in a similar manner, when the control ring It is adjusted to its finalposition. with the edge it thereof properly spaced from the edge B3 of vthe piston flange lli, when the valve is seated,

the ring it is locked in position by a lock pin tu entering flutes tl inthev periphery of the ring it.

From the foregoing description it will be clear that the valve of thepresent invention provides a number of advantages over the safety valvesin current use, which may be catalogued as follows.

I. High lift resulting from:

(A) Reversal of flow of pressure fluid by baille constituted by the headsurface 2l of the piston 2d and its extended skirt 25, and theemployment ci the reactive force of the jet thus produced. Y

(B) Closing-ofi of the relief ports et of the name 2l-2l near the end ofthe lift, whereby accumulation and increase of pressure under the bailleis developed.

(C) Automatically variable baille which increases the eiective area ofthe baille 'lllA surface during progression o t litt result-` -lns ingreater total pressure at and near .the end of the lii't. II. Lowblow-down due to:

(A) Ported pistonbailie which releases accu- (1?.) Automaticallyvariable baille area. which l decreases the eiiective area of the baillesurface during closing vmovement of the valve resulting in a loweredtotal pressure as the valve closes.

III. Stability resulting from:

(A) Large dierential between the force acting under the piston at thestart oi the lift and the force exerted .under it at accumulatedpressure near the end ot the lift. i

(B) Large dierential between the force acting under the piston atmaximum lift and the force exerted under it at any predeterminedpressure at which the valve is to close.

(C) Relatively low capacity at set=pressure lift and high capacity ataccumulated pressure litt, whereby the valve laprevented fromover-discharging at low accumule-tions, and whereby resultant .e uaction is eliminated.

TV. improved pressure-vessel protection:

ecause of the characteristics noted inlH (C), any system including andprotected A by the valve oi the present invention will,

not be subjected to injurious pressure liuctuations resulting fromsudden and violent releases or or changes in pressure. V. Less stress onseating surfaces of valve:

Because, at the close-oil' pressure, the piston has shorter distance totravel. VI. Hielo. discharge capacity.

liet ular surface on said piston and, except `when substantially fullyopen, extending there- :from axially beyond the plane of the annularsurface encircling said seat in radially spaced outwardly flaringrelation to the cuter peripheral edge of the seat-encircling surface, anormally open circumerntially extending cavity formed in said piston inaxially spaced relation to the plane ci said hat annular surfacethereof, meansinternally of the piston adording communication betweensaid cavity and said piston annular surface, a cylindrical guide forsaid piston, said cavity and said guide having cooperating peripheraledges adapted to overlap and close said cavity under predetermined axialmovement of said pis-y ton relative to said cuide and said valve seat.

2. A pressure relief valve comprising a hollow body, a cylindricalpiston guide carried by and extending into said hollow body, a pistonreclp roeanle in said guidavan annular valve seatin said body in a planespaced axially from the plane of the inner end of said guide; anannular` seatengaging surface on the inner end of said piston, saidseat-engaging surfacewhen lifted from' said seat forming' an annularyescape port for' Y forming'a progressively variable-area port with theperipheral edge of the uiar surface en circling said seat, a normallyopen annular external recess formed :in thel outer surfaceJ of lsaidpiston above said dat annular surface thereon,

one peripheral side edge of said recess forming a variable area cut-oilport with Athe inner peripheral edge of said guide, and internal portsformed in said piston and extending from said recess tol said annularsurface on said piston end said internal ports and recess affordingescape of tiuid from the region intermediate said flat annular lsurfaces to the exterior of the piston above said baille.

